Fluid filter

ABSTRACT

A spring  15  is crimpingly fixed to an element holding plate  14  of the fluid filter. Since the spring  15  is crimpingly fixed to the element holding plate  14,  a material having a high elastic limit can be freely selected for the spring  15.  At the assembling time, the spring  15  can be prevented from yielding to be elastically deformed, even when the size between the upper end of the element  12  and the crest of the filter case  11  fluctuates. As a result, it is possible to provide a fluid filter which requires no high sizing accuracy of the individual parts composing the fluid filter at the assembling time so that it can be easily assembled.

CROSS REFERENCE TO RELATED APPLICATION

This is the 35 USC 371 national stage of international applicationPCT/JP99/03097, filed on Jun. 10, 1999, which designated the UnitedStates of America.

BACKGROUND OF THE INVENTION

The present invention relates to a fluid filter for filtering the oil ofan automobile or the like.

The recycling consciousness enhanced in recent years has demanded therecovery of used oil filters for classified materials even when the oilfilters are disposed of. We have proposed a vehicular fluid filter shownin FIG. 9 (in Japanese Patent Application No.HEI 9-260542) as an oilfilter capable of classifying and recovering a cylindrical element offilter paper from a metallic inner cylinder holder.

An element 1 is assembled in a removable manner around an inner cylinderholder 2. On the lower end of the inner cylinder holder 2, there isaxially press-fitted a flange portion 3 for supporting the lower end ofthe element 1. An element holding plate 4 is placed on the upper elementend. At the inner side of the element holding plate 4, there is formed afitted portion 4 a to be fitted on the upper end of the inner cylinderholder 2. At the outer side of the element holding plate 4, there isformed a fitted portion 4 a to be fitted on the upper end of the innercylinder holder 2. At the outer side of the element holding plate 4,there is formed a pressure portion 4 b for holding the upper end of theelement 1. A relief valve 6 is projection-welded to the lower face ofthe element holding plate 4. Between the upper face of the pressureportion 4 b of the element holding plate 4 and the crest of a filtercase 5, there is sandwiched a check spring 4 c. This check spring 4 c isprojection-welded to the element holding plate 4. The force of thepressure portion 4 b for holding the element is generated when the checkspring 4 c is bent and deformed by the abutment against the crest of thefilter case 5. The element 1 is axially sandwiched at its lower end bythe flange portion 3 and at its upper end by the pressure portion 4 b.

In the vehicular fluid filter of the prior art, however, the checkspring 4 c is projection-molded to the element holding plate 4.Therefore, the check spring 4 c and the element holding plate 4 have tobe made of weldable materials, but a material having a high elasticlimit cannot be used for the check spring 4 c. When the vehicular fluidfilter is to be assembled, therefore, the height sizes of the individualparts composing the vehicular fluid filter have to be too accurate toprovide a vehicular fluid filter of easy assembly.

Since the leading end of the inner cylinder holder 2 is cut sharp, onthe other hand, it may be caught by the inner circumference of theelement 1 when this element 1 is to be assembled with the inner cylinderholder 2 thereby to damage the inner circumference of the element 1.Therefore, this element 1 has to be carefully assembled with the innercylinder holder 2.

Since the inner cylinder holder 2 and the flange portion 3 are composedof separate pieces, moreover, there is demanded not only the step ofpress-fitting the inner cylinder holder 2 axially onto the flangeportion 3 but also a sizing accuracy for each part. This requires a stepof forming each part highly accurately and press-fitting it so that avehicular fluid filter of easy assembly cannot be provided.

SUMMARY OF THE INVENTION

It is, therefore, an object of the invention to provide a vehicularfluid filter of easy assembly.

According to one aspect of the invention, there is provided a fluidfilter comprising: a cylindrical filter case having a lower end opened;a cylindrical element to be inserted into the filter case; an innercylinder holder to be so assembled in the inner circumference of theelement that the element can be extracted; an element holding platefitted on the upper end of the inner cylinder holder for holding theupper end of the element; and a spring fixed on the element holdingplate for urging the element holding plate elastically to the upper endof the element, wherein the element holding plate and the spring arecrimpingly fixed.

Since the element holding plate and the spring are crimpingly fixed,according to this aspect, they can be jointed to each other even if theyare made of different materials. Since a material having a higherelastic limit than that of the element holding plate can be freelyselected for the spring, the spring can yield to prevent the plasticdeformation even when the size between the upper end of the element andthe filter case fluctuates. At the assembling time, therefore, theheight sizes of the individual parts composing the vehicular fluidfilter need not be accurate, and it is possible to provide a vehicularfluid filter of easy assembly.

According to this aspect, the spring steel is used for the check springso that an elastic limit can be enlarged.

According to another aspect of this invention, the fluid filter furthercomprises a relief valve device welded to the element holding plate foracting according to the difference between the inside and outsidepressures of the element, wherein the spring is crimpingly fixed at aportion different from the welded position of the relief valve device.

According to this aspect, the spring is crimpingly fixed at a portiondifferent from the welded position of the relief valve device so thatthe fluid filter can be easily manufactured without being damaged at thewelded portion at the crimping step.

According to another aspect of this invention, the spring includes leafspring portions extended and protruded from the portion crimpingly fixedto the element holding plate so that the element holding plate is urgedto the upper end of the element by the elastic force which is generatedby bringing the warped leaf spring portions into abutment against thefilter case.

According to this aspect, the element holding plate is urged by bringingthe warped leaf spring portions into abutment against the filter case,so that the number of parts can be reduced.

According to this aspect, the inner cylinder holder is curved at its endportion so that the inner cylinder holder can be smoothly assembled inthe inner circumference of the element without damaging the innercircumference of the element.

According to this aspect, the end portion of the inner cylinder holderis curved by folding it inward so that its structure is not complicatedwhile enhancing the strength of the inner cylinder holder.

According to this aspect, the inner cylinder holder is molded of asynthetic resin so that its end portion can be easily curved.

According to this aspect, the end portion of the inner cylinder holderis diametrically reduced at its end portion so that it can be smoothlyassembled in the inner circumference of the element without damaging theinner circumference of the element.

According to this aspect, the inner cylinder holder is molded integrallywith the flange portion so that the number of parts can be reduced whileeliminating the step of press-fitting the inner cylinder holder axiallyonto the flange portion, to facilitate the assembly and to enhance thestrength of the inner cylinder holder by the flange portion.

According to another aspect of this invention, there is provided a fluidfilter comprising an inner cylinder holder to be so assembled with theinner circumference of an element that the element can be extracted,wherein the fluid filter further comprises: a plate member arranged onthe side of the end portion of the inner cylinder holder; and a packingsandwiched between the end portion of the inner cylinder holder and theplate member for establishing a seal between the end portion of theinner cylinder holder and the plate member, and wherein the end portionof the inner cylinder holder is molded integrally with the innercylinder holder.

According to this aspect, the number of parts can be reduced whilefacilitating the assembly by molding the end portion integrally with theinner cylinder holder.

According to another aspect of this invention, there is provided a fluidfilter comprising an inner cylinder holder to be so assembled with theinner circumference of an element that the element can be extracted,wherein the outer circumference of the inner cylinder holder, asconfronting the inner circumference of the element, is formed in unevenshape and has openings formed at the places other than the ridges of theouter circumference for providing communication between the inside andoutside of the inner cylinder holder.

According to this aspect, the inner circumference of the element iscontacted only by the ridges formed on the outer circumference of theinner cylinder holder so that the inner cylinder holder can be easilyassembled with little resistance. As a result, the open area of theinner circumference of the element can be substantially enlarged toreduce the flow resistance and lower the flow velocity at the openingsthereby to improve the filtering efficiency.

According to another aspect of this invention, there is provided a fluidfilter comprising: a cylindrical element; an inner cylinder holder to beso assembled in the inner circumference of the element that the elementcan be extracted; an element holding plate fitted on the end portion ofthe inner cylinder holder for holding the upper end of the element; anda relief valve device attached to the element holding plate for actingaccording to the difference between the inner and outer pressures of theelement, wherein said relief valve device is arranged in the innercircumference of the element so that it can be used as a guide forinserting the relief valve device into the inner cylinder holder bybringing the inner circumference of the inner cylinder holder intoabutment against the outer circumference of the relief valve device.

According to this aspect, when the inner cylinder holder is to beinserted into the element, the relief valve device can be utilized as aguide for inserting the inner cylinder holder thereby to smoothen theassembly.

According to another aspect of this invention, there is provided a fluidfilter comprising: a cylindrical element; an inner cylinder holder to beso assembled in the inner circumference of the element that the elementcan be extracted; an element holding plate fitted on the end portion ofthe inner cylinder holder for holding the upper end of the element; anda relief valve device attached to the element holding plate for actingaccording to the difference between the inner and outer pressures of theelement, wherein said relief valve device is arranged in the innercircumference of the element so that it can regulate the position of theinner cylinder holder for assembling the relief valve device into theinner cylinder holder by bringing the inner circumference of the innercylinder holder into abutment against the outer circumference of therelief valve device.

According to this aspect, when the inner cylinder holder is assembledinto the element, the relief valve device can be utilized as a memberfor positioning the inner cylinder holder thereby to improve theassembling accuracy.

According to another aspect of this invention, the crimped portion onthe holding plate is crimpingly fixed on the spring.

According to this aspect, the crimped portion is crimped on the holdingplate so that the yield of the spring can be improved (better than thecase where the crimped portion is formed on the spring side). Even if amaterial having a higher elastic limit than that of the holding plate isfreely selected for the spring, moreover, the crimping works can befacilitated to retain the crimping accuracy.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a section showing a vehicular fluid filter of a firstembodiment;

FIG. 2 is a top plan view showing a check spring;

FIG. 3 is a section showing an inner cylinder holder to be used in avehicular fluid filter of a second embodiment;

FIG. 4 is a section showing a vehicular fluid filter of a thirdembodiment;

FIG. 5 is a section showing an inner cylinder holder to be used in avehicular fluid filter of a third embodiment;

FIG. 6 is a section showing a vehicular fluid filter of a fourthembodiment;

FIG. 7 is a section showing an inner cylinder holder to be used in avehicular fluid filter of a fourth embodiment;

FIG. 8(A) is a top plan view showing the inner cylinder holder of thevehicular fluid filter of the third embodiment and taken along line A—Aof FIG. 8(B);

FIG. 8(B) is a section showing the vehicular fluid filter and takenalong line B—B of FIG. 8(A); and

FIG. 9 is a section showing a vehicular fluid filter of the prior art.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[First Embodiment]

With reference to FIGS. 1 and 2, here will be described a firstembodiment of the vehicular fluid filter according to the invention.

As shown in FIG. 1, the vehicular fluid filter is constructed toinclude: a filter case 11 having a cylindrical container shape opened atits lower end; a cylindrical element 12 fitted in the filter case 11 forfiltering oil; an inner cylinder holder 13 fitted on the innercircumference of the element 12; an element holding plate 14 for holdingthe element 12 downward; and a check spring 15 for applying a pushingforce to the element holding plate 14. At the lower end of the innercylinder holder 13, there is formed a flange portion 16 for supportingthe lower end of the element 12. This element 12 is axially sandwichedbetween the element holding plate 14 and the flange portion 16. At thelower end of the filter case 11, there is disposed an end plate 17 whichis threaded to be mounted on the engine block. Between the end plate 17and the flange portion 16, there is sandwiched a packing 23. To theouter circumference of the lower face of the end plate 17, there isfixedly welded a closure plate 18. This closure plate 18 is fixedlywound on the open end of the filter case 11. In the closure plate 18,there is mounted a packing 19 which is closely fitted in the engineblock.

The element 12 is formed generally into a cylindrical shape by folding asheet of treated paper repeatedly. The ridges of the folds provide theouter circumference of a cylinder, and the valleys provide the innercircumference. To the inner circumferences of the upper end and lowerend of the element 12, there are bonded seal plates 20 a and 20 b by anadhesive. Since the filter paper is folded, the element 12 is enlargedits total area for passing the oil while lowering the flow resistance.

The inner cylinder holder 13 is so assembled in the inner circumferenceof the element 12 that it can be extracted. This inner cylinder holder13 is formed into a cylindrical shape having a small thickness and anexternal diameter substantially equal to that of the inner circumferenceof the element 12. The leading end of the inner cylinder holder 13 iscut away at its edge and is curled inward by a press or the like. In thelower end of the inner cylinder holder 13, on the other hand, there isaxially press-fitted the flange portion 16. This flange portion 16 isbulged at its outer circumference into a flange shape all over the outercircumference of the inner cylinder holder 13. In the circumference ofthe inner cylinder holder 13, there are opened a plurality of passageports 21 for the filtered oil to flow out therethrough to the cleanside. Here, the leading end of the inner cylinder holder 13 need not becurled into the round shape but may be bent to have curved face.

The element holding plate 14 is made of a generally disc-shaped sheetand is opened at its central portion to have an opening 14 a. Around theopening 14 a, there is formed a downward ridge 14 b. Around this ridge14 b, there is formed a step 14 c. This step 14 c is fitted at its innerwall face on the inner cylinder holder 13. Around the step 14 c, thereis formed a pressure portion 14 d at a lower level.

On the lower face of the element holding plate 14, there is mounted arelief valve device 22. This relief valve device 22 is provided with: acylindrical case 22 a welded through a flange to the lower face of theelement holding plate 14; a plate 22 b capable of abutting against theridge 14 b; and a compression spring 22 c sandwiched between the lowerface of the plate 22 b and the inside bottom face of the case 22 a, asshown in FIG. 1. At an ordinary time, the plate 22 b is urged to abutagainst the ridge 14 c by the compression spring 22 c thereby to holdthe element holding plate 14 and the plate 22 b in close contact. Whenthe difference in the pressure between the clean side and the dirty sideexceeds a predetermined value, the plate 22 b is pushed downward againstthe urging force of the compression spring 22 c to establish a clearancebetween the element holding plate 14 and the plate 22 b. Since the oilof the dirty side flows through that clearance to the clean side, it ispossible to prevent a trouble that the difference between the inside andoutside pressures to be applied to the filter paper grows so large as tobreak the filter paper.

This check spring 15 is composed, as shown in FIG. 2, of an annularflange portion 15 a fitted on the upper face of the pressure portion 14d, and four leaf spring portions 15 b formed integral with the flangeportion 15 a. Since these four leaf spring portions 15 b are arranged ontwo parallel lines extending tangentially of the annular flange portion,the check spring 15 can be stably mounted in the filter case 11 with anexcellent production yield. Since the leading end portions of the leafspring portions 15 b are formed to match the contour of the inner faceof the filter case 11, moreover, the stability at the mounted time canbe further improved. The leaf spring portions 15 b are formed by foldinga sheet material. On the other hand, the check spring 15 is fixedlysecured on the element holding plate 14 by bending ears 14 e, as formedat the two ends of the element holding plate 14, to clamp itself. Thepositions where the check spring 15 is fixedly secured are set differentfrom the positions W where the case 22 a is welded to the elementholding plate 14. As a result, the welded portions are not damaged bythe securement treatment.

Since the secured portion formed on the outer circumference of theelement holding plate is secured and fixed on the spring, the abuttingportion (or seal portion) between the ridges 14 b of the element holdingplate and the plate 22 b of the relief valve device can be preventedfrom deforming, to improve the contacting accuracy (or sealing property)inbetween.

Moreover, since the four leaf spring portions 15 b are secured and fixedat their roots, the stability for mounting the spring in the filter caseis improved. Since the two leaf spring portions arranged on a commonstraight line are secured and fixed at their central portions, moreover,the number of portions to be secured can be reduced while stabilizingthe spring characteristics of the two leaf springs. Since the securedportions are not only different from but also the most distant from thewelded portions W where the element holding plate and the relief valvedevice are welded, still moreover, the welded portions are not damagedat the securement step, and the securement works and the welding workscan be simultaneously performed to improve the workability.

The check spring 15 is made of spring steel different from that of theelement holding plate 14. When the leaf spring portions 15 b come intoabutment against the inner bottom of the filter case 11, they aredeformed to apply the pressure to the pressure portion 14 d. When theleaf spring portions 15 b are inserted into the filter case 11, on theother hand, the element holding plate 14 is positioned generally at thecenter of the filter case 11. Here, the check spring 15 of FIG. 1 isshown in section taken along line A—A of FIG. 2.

By the elastic forces of the leaf spring portions 15 b interposedbetween the element holding plate 14 and the filter case 11, as shown inFIG. 1, the pressure portion 14 d of the element holding plate 14 pushesthe seal plate 20 a at the upper end of the element 12. As a result, thecontact between the seal plate 20 a and the pressure portion 14 d isenhanced to prevent the oil leakage. By the pressure of the elementholding plate 14, on the other hand, the seal plate 20 b at the lowerportion of the element 12 comes into close contact with the flangeportion 16 of the inner cylinder holder 13. Between the inner cylinderholder 13 and the end plate 17, on the other hand, there is sandwichedthe packing 23 so that the oil leakage is also prevented.

The element holding plate may preferably be made of a material having alower elastic limit than that of the check spring. The workability isexcellent especially when an SP material or the like is used.

The end plate 17 is provided with an oil inlet port 24 in its outercircumference and an oil outlet port 25 at its center. The oil, assupplied from the oil pump, flows inward from the oil inlet port 24. Theoil flowing in the vicinity of the outer circumference of the filtercase 11 is cleared of dust of small particle by the element 12 and flowsout of the oil outlet port 25 through the passage ports 21 formed in theinner cylinder holder 13. Here, the packing 23 overlying the oil inletport 24 has an additional function as a check valve. As a result, theoil is prevented from flowing backward or leaking to the outside whenthe engine is stopped or when the oil filter is removed.

Here will be described a method of assembling one embodiment of thevehicular fluid filter thus far described. First of all, the leading endof the inner cylinder holder 13 is gradually inserted so far into theinner circumference of the element 12 as to reach the position of theflange portion 16. Since the leading end of the inner cylinder holder 13is curled round, the inner cylinder holder 13 can be smoothly assembledin the inner circumference of the element 12 while preventing the innercircumference of the element 12 from being damaged by the sharp leadingend, if any, and while enhancing the strength of the inner cylinderholder 13. Even when the leading end is bent to have a curved facealthough not curled round, on the other hand, the inner cylinder holder13 can also be smoothly assembled while enhancing its strength. Here,the leading end of the inner cylinder holder 13 is rounded so that it isgradually guided by the curved face to slide into the element holdingplate 14 even if slightly offset from the element holding plate 14. As aresult, the inner cylinder holder 13 can be easily assembled with theelement holding plate 14. To the element holding plate 14, there arefixed in advance the relief valve device 22 by the welding method andthe check spring 15 by the securement method.

Next, the integrated structure of the element 12, the inner cylinderholder 13 and the element holding plate 14 is inserted into the filtercase 11. Then, the packing 23 is attached to the lower end of the innercylinder holder 13, and the closure plate 18, to which the end plate 17is fixedly welded, is fixedly wound on the open end of the filter case11. At this time, the size of the clearance between the upper end of theelement 12 and the crest of the filter case 11 may be fluctuated by thewinding height or the like of the closure plate 18. Since the checkspring 15 made of the spring steel having a large elastic limit isfixedly secured to the element holding plate 14, the check spring 15 canbe prevented from easily yielding to deform plastically, even with thefluctuation in the size of the clearance between the upper end of theelement 12 and the crest of the filter case 11. As a result, it ispossible to provide a vehicular fluid filter which can be easilyassembled while requiring no high accuracy for the height sizes of theindividual parts composing the fluid filter at their assembling time.The leaf spring portions 15 b are bent by their abutment against thecrest of the filter case 11. By the elastic forces of the leaf springportions 15 b, the element 12 is sandwiched in the vertically closecontact. Here, the check spring 15 is made of the spring steel so thatit can be prevented from being permanently set, to improve its function.

The secured portion of the holding plate may be fixed on the spring, andthe secured portion of the spring may also be fixed on the holdingplate. This modification is advantageous because the number of parts isnot increased. Through the rivets or the like, however, the holdingplate and the spring may be secured and fixed.

[Second Embodiment]

FIG. 3 shows a second embodiment of the fluid filter according to theinvention. The components corresponding to those of the first embodimentwill be omitted in connection with their descriptions by designatingthem by the common reference numerals.

An inner cylinder holder 30 to be used in the filter of the secondembodiment is molded of a synthetic resin integrally with a flangeportion 30 b at its lower portion. The upper end 30 c and the lower end30 d of the inner cylinder holder 30 are molded round. In this innercylinder holder 30, there are formed thin oil passage slits 31 in thecircumferential direction.

In the rounded lower end 30 d, there is fitted a packing.

To the lower end 30 d, moreover, there is applied through the packing anend plate which corresponds to the end plate 17 of the first embodiment.

Since the flange portion 30 b and the lower end 30 d are thus moldedintegrally with the inner cylinder holder 30, the number of parts can bereduced, and the step of press-fitting the flange portion axially in theinner cylinder holder 30 can be eliminated to facilitate the assembly.

Since the inner cylinder holder 30 is molded to have the round upper end30 c, on the other hand, it can be smoothly assembled like the curledinner cylinder holder 13 without damaging the inner circumference of theelement 12.

[Third Embodiment]

Here will be described a third embodiment of the fluid filter accordingto the invention with reference to FIGS. 4 and 5. The componentscorresponding to those of the first embodiment will be omitted inconnection with their descriptions by designating them by the commonreference numerals.

In the third embodiment, as shown in FIGS. 4 and 5, an inner cylinderholder 130 is made smaller in the external diameter of its leading endportion 130 a than that of its central portion 130 b. Moreover, theouter circumference of the central portion 130 b of the inner cylinderholder 130, as formed to have a diameter substantially equal to theinternal diameter of the element 12, is confronted by the innercircumference of the element 12.

In the third embodiment, the inner cylinder holder 130 is diametricallyreduced at its leading end portion 130 a so that its leading end 130 ais kept away from contact with the inner circumference of the element 12when it is inserted into the element 12. As a result, the fluid filtercan be smoothly assembled without damaging the element 12. On the otherhand, the leading end portion 130 a may also be diametrically reduced bytapering it. Here, the constructions of the first and third embodimentsmay be modified such that the lower end side of the inner cylinderholder 13 or 130 is curved or diametrically reduced. Then, the innercylinder holder can also be smoothly assembled like the first and thirdembodiments without damaging the inner circumference of the element, ifit is inserted from its lower end portion into the element.

[Fourth Embodiment]

Here will be described a fourth embodiment of the fluid filter accordingto the invention with reference to FIGS. 6 and 7. The componentscorresponding to those of the first embodiment will be omitted inconnection with their descriptions by designating them by the commonreference numerals.

In the fourth embodiment, as shown in FIGS. 6 and 7, an inner cylinderholder 230 is integrally molded of a synthetic resin. In the innercylinder holder 230, as shown in FIG. 7, there are formed a number ofoil passage slits 231 for providing communication between the inside andoutside of the inner cylinder holder 230. These slits 231 function likethe oil passage slits 31 of the second embodiment.

The inner cylinder holder 230 is made to have an external diametersubstantially equal to the internal diameter of the element 12 so thatits outer circumference 234 is arranged, when assembled, along the innercircumference of the element 12. A flange portion 234 a, as protrudedfrom the outer circumference 234, functions like the flange portion 30 a(of FIG. 2) in the second embodiment.

On the inner circumference of the inner cylinder holder 230, on theother hand, there are formed protrusions 235 which are protruded in theaxial direction of the inner cylinder holder 230, as shown in FIG. 7.These protrusions 235 are formed by a making the inner cylinder holder230 thicker at its upper portion so that the internal diameter of theupper portion of the inner cylinder holder 230 is made smaller than thatof the inner circumference 236 of the lower portion. As shown in FIG. 6,the internal diameter of the inner cylinder holder 230 at the portionwhere the protrusions 235 are formed is made slightly larger than theexternal diameter of the case 22 a of the relief valve device 22.

Thus in the fourth embodiment, the inner cylinder holder 230 is providedwith the protrusions 235 at its upper portion, as compared with itslower portion, to have an internal diameter slightly larger than thecase 22 a. As a result, this case 22 a is enabled to function as a guidefor guiding the element 12 so that the inner cylinder holder 230 can beinserted in contact with the case 22 a into the element 12. Thisguidance can smoothen the assembling works more.

In the fourth embodiment, on the other hand, the position of the innercylinder holder 230 assembled is regulated by the case 22 a. In otherwords, this case 22 a can be utilized for centering the inner cylinderholder 230. Moreover, the thicker portions are formed at the upperportion of the inner cylinder holder so that they can enhance thestrength of the inner cylinder holder. This centering function canimprove the assembling accuracy.

[Fifth Embodiment]

Here will be described a fifth embodiment of the fluid filter accordingto the invention with reference to FIGS. 8(A) and 8(B). The componentscorresponding to those of the first embodiment will be omitted inconnection with their descriptions by designating them by the commonreference numerals.

In the fifth embodiment, an inner cylinder holder 330 is integrallymolded of a synthetic resin. In the inner cylinder holder 330, there areformed a number of oil passage slits 331 for providing communicationbetween the inside and outside of the inner cylinder holder 330. Theseslits 331 function like the oil passage slits 31 of the secondembodiment.

On the outer circumference of the inner cylinder holder 330, there areformed protrusions 332, protrusions 333, protrusions 334 and protrusions335, as designated downward in the recited order in FIG. 8(B). As shownin FIG. 8(A), the protrusions 332 to 335 are individually arranged inplurality (e.g., twelve) radially of the axis of the inner cylinderholder 330. At the portions of the protrusions 332 to 335, as shown inFIG. 8(B), the inner cylinder holder 330 is made to have an externaldiameter substantially equal to the internal diameter of the element 12so that the outer circumferences of the protrusions 332 to 335 can abutagainst the inner circumference of the element 12. From the protrusions335, on the other hand, there is formed a flange portion 335 a which isbulged from the outer circumferences of the protrusions 335. This flangeportion 335 a corresponds to the flange portion 30 a (of FIG. 2) in thesecond embodiment.

In the fifth embodiment, the outer circumference of the inner cylinderholder 330 is corrugated by forming the protrusions 332 to 335.Moreover, the inner circumference of the element 12 is contracted onlyby the outer circumferences of the protrusions 332 to 335 having smallareas but not directly by the oil passage slits 331 located in therecesses. As a result, the substantial open area of the innercircumference of the element 12 can be enlarged so that the reduction offlow resistance and the flow speed at the open area resulting in theimprovement of the filtering efficiency. On the other hand, the strengthof the inner cylinder holder 330 can be enhanced by corrugating itsouter circumference.

As shown in FIG. 8(B), the inner cylinder holder 330 has an internaldiameter slightly larger than the external diameter of the case 22 a ofthe relief valve device 22 so that the case 22 a not only functions as aguide for the assembling works but also is utilized for centering theinner cylinder holder 330. As a result, the smooth assembly can be madein an improved accuracy.

In the outer circumference of the end plate 17, there is formed anexternal thread 17 a, through which the end plate 17 is fastened by aring nut 341. By screwing this ring nut 341 on the end plate 17, thefilter case 11 and the end plate 17 are fastened to each other throughan O-ring 342. Here in the filter case 11, there is formed a protrusion11 a to be fitted in a notch formed in the outer circumference of theend plate 17. This protrusion 11 a functions as a rotation stopperbetween the filter case 11 and the end plate 17. Thus, the element canbe replaced by a new one in the case of the filter using the ring nut.

When the inner cylinder holder is made of a synthetic resin, the moldingis easy. However, the inner cylinder holder may be made of not only thesynthetic resin but also another material such as aluminum. If themolding material is the synthetic resin or aluminum, it contributes to alightening of weight.

According to one embodiment of this invention, since the element holdingplate and the spring are crimpingly fixed, they can be jointed to eachother even if they are made of different materials. Since a materialhaving a higher elastic limit than that of the element holding plate canbe freely selected for the spring, the spring can yield to prevent theplastic deformation even when the size between the upper end of theelement and the filter case fluctuates. At the assembling time,therefore, the height sizes of the individual parts composing thevehicular fluid filter need not be accurate, and it is possible toprovide a vehicular fluid filter of easy assembly.

According to another embodiment of this invention, the inner cylinderholder is curved at its end portion so that the inner cylinder holdercan be smoothly assembled in the inner circumference of the elementwithout damaging the inner circumference of the element.

According to another embodiment of this invention, the end portion ofthe inner cylinder holder is diametrically reduced at its end portion sothat it can be smoothly assembled in the inner circumference of theelement without damaging the inner circumference of the element.

According to another embodiment of this invention, the inner cylinderholder is molded integrally with the flange portion so that the numberof parts can be reduced while eliminating the step of press-fitting theinner cylinder holder axially onto the flange portion, to facilitate theassembly and to enhance the strength of the inner cylinder holder by theflange portion.

According to another embodiment of this invention, the number of partscan be reduced while facilitating the assembly by molding the endportion integrally with the inner cylinder holder.

According to another embodiment of this invention, the innercircumference of the element is contacted only by the ridges formed onthe outer circumference of the inner cylinder holder so that the innercylinder holder can be easily assembled with little resistance. As aresult, the open area of the inner circumference of the element can besubstantially enlarged to reduce the flow resistance and lower the flowvelocity at the openings thereby to improve the filtering efficiency.

According to another embodiment of this invention, when the innercylinder holder is to be inserted into the element, the relief valvedevice can be utilized as a guide for inserting the inner cylinderholder thereby to smoothen the assembly.

According to another embodiment of this invention, when the innercylinder holder is assembled into the element, the relief valve devicecan be utilized as a member for positioning the inner cylinder holderthereby to improve the assembling accuracy.

What is claimed is:
 1. A fluid filter comprising: a cylindrical filtercase having a lower open end; a cylindrical element inserted into thefilter case; an inner cylinder holder assembled with an innercircumference of the element such that the element can be extracted; ametallic element holding plate fitted on an upper end of the innercylinder holder for holding an upper end of the element; and a metallicspring fixed on the metallic element holding plate for urging themetallic element holding plate elastically to the upper end of theelement; wherein the metallic element holding plate and the metallicspring are crimpingly fixed together by bending at least one ear portionformed on the metallic element holding plate to clamp the metallicspring; and the metallic spring includes at least one leaf springportion which extends and protrudes from a portion fixed to the metallicelement holding plate.
 2. The fluid filter according to claim 1, whereinthe metallic spring is made of spring steel.
 3. The fluid filteraccording to claim 1, further comprising: a relief valve device weldedto the metallic element holding plate at a position, said relief valveacting according to the difference between the inside and outsidepressures of the element; and wherein the metallic spring is crimpinglyfixed at a portion different from the welded position of the reliefvalve device.
 4. The fluid filter according to claim 1, wherein themetallic spring includes a plurality of said leaf spring portionsextended and protruded from the portion crimpingly fixed to the metallicelement holding plate so that the metallic element holding plate isurged to the upper end of the element by an elastic force which isgenerated by bringing warped leaf spring portions into abutment againstthe filter case.
 5. The fluid filter according to claim 1, wherein theinner cylinder holder is curled into round shape at its end portion sothat the inner cylinder holder is inserted from its end portion into theelement.
 6. The fluid filter according to claim 5, wherein the endportion of the inner cylinder holder is curled inwardly.